NASA has selected a Planetary Science Institute proposal to investigate the Marius Hills Pit on the moon, deploying radar, seismic instruments, and gravity sensors to determine whether the volcanic opening leads to a subterranean lava tube that could shelter future lunar base crews.
The search for underground habitable spaces on the moon is moving from orbital observation to direct surface exploration. NASA selected the Geophysical Instruments for Marius Lunar Pit Investigation (GIMLI) under its Payloads and Research Investigations on the Surface of the Moon program, according to agency announcements. The project aims to probe a gaping hole known as the Marius Hills Pit, located in one of the lunar surface’s most volcanically diverse regions.
Discovered in 2009 by Japan’s SELENE spacecraft, the pit plunges roughly as deep as a 10-story building with an opening approximately the size of an American football field. Planetary scientists calculate the opening measures about 213 by 295 feet across and between 34 and 45 meters deep. While roughly 300 such pits have been identified across the moon, researchers suspect this particular feature serves as a skylight where the roof of an ancient lava tube collapsed.
Instruments Deployed to Probe the Marius Hills Pit
To peer beneath the rugged terrain, the GIMLI team will combine three distinct geophysical methods: ground-penetrating radar, seismic sensors, and a gravimeter to measure local gravitational pull. These instruments will be mounted on a lander and rover delivered to the lunar surface through NASA’s Commercial Lunar Payload Services initiative. Cameras will simultaneously capture views of the surrounding terrain and the exposed walls of the pit.
International and industrial partners are contributing specialized hardware to the mission. Honeybee Robotics, a subsidiary of Blue Origin, will help build the equipment and instrumentation, including seismic sensors and the gravimeter. Meanwhile, the Norwegian Space Agency is supplying the mission’s ground-penetrating radar.
Reviving Active-Source Seismic Surveys on the Moon
For the researchers leading the proposal, the mission represents a rare chance to gather subsurface acoustic data that has gone largely uncollected for decades. Than Putzig, an associate director and senior scientist at the Planetary Science Institute who serves as the project’s lead, noted the technical milestone.
It’s long been a desire of mine to reintroduce intentional active-source seismic methods to planetary science, as it has essentially not been done since the Apollo astronauts conducted the first seismic surveys on the moon.
Than Putzig, associate director and senior scientist at the Planetary Science Institute
By recording how sound waves travel through the subsurface strata, the seismometers will help map internal density changes and void spaces. Amanda Hendrix, PSI’s director and CEO, noted in a statement that GIMLI represents the type of ambitious planetary science that the organization was built to pursue. Gareth Morgan, a senior scientist and deputy principal investigator on the program, emphasized the broader geological significance of finding a cavity.
Confirming a substantial lava tube would give us an insight into how volcanism operated on the moon. Lava tubes are a common feature of basaltic volcanism on Earth, so identifying them on the moon means we could use knowledge of such terrestrial caves to better understand lunar history.
Gareth Morgan, PSI Senior Scientist and Deputy Principal Investigator
Brad Bailey noted that the selections showcase how Artemis and the Moon Base initiative are expanding the frontier of lunar exploration, advancing innovative technologies, deepening our understanding of the lunar environment, and paving the way for future astronaut missions.
Natural Bunkers for Future Astronaut Outposts
Beyond answering questions about ancient volcanic activity dating back between 3.8 and 3 billion years, confirming an underground cavern carries practical implications for human settlement. Space agency planners view subsurface tunnels as potential natural habitats that could shield incoming crews from surface radiation levels. Natural rock ceilings could also mitigate extreme temperature swings, protect against micrometeorite impacts, and reduce the heavy engineering burden of building entirely surface-level radiation shelters.
The investigation is one of three PRISM selections announced by NASA to prepare infrastructure for the Moon Base Program, which targets a permanent habitable outpost at the lunar South Pole in the early 2030s. The other two selected missions focus on mapping hidden water ice deposits in micro-cold traps and monitoring environmental hazards like moonquakes and micrometeoroid strikes. NASA has not yet released firm launch dates for any of the three payloads.